Acoustical and thermal insulators and liners for application to vehicles are well known in the art. These insulators typically rely upon both sound absorption, i.e. the ability to absorb incident sound waves and transmission loss, i.e. the ability to reflect incident sound waves, in order to provide sound attenuation. They also rely upon thermal shielding properties to prevent or reduce the transmission of heat from various heat sources (e.g. engine, transmission and exhaust system), to the passenger compartment of the vehicle. Such insulation is commonly employed as an under carpet heat shield and a floor pan insulator.
Examples of acoustical and thermal insulation in the form of liners are disclosed in a number of prior art patents including U.S. Pat. No. 4,851,283 to Holtrop et al. and U.S. Pat. No. 6,008,149 to Copperwheat. As should be apparent from a review of these two patents, engineers have generally found it necessary to construct such liners from a laminate incorporating (a) one or more layers to provide the desired acoustical and thermal insulating properties and (b) one or more additional layers to provide some rigidity to allow ease of handling during installation.
U.S. Pat. No. 6,092,622 to Hiers et al. and U.S. Pat. No. 6,123,172 to Byrd et al. disclose needled composite thermal and acoustical insulators containing various layers of polymer fibers, glass fibers, metallic foils, scrims and other facings. The metallic foil facing is secured in place with an adhesive. The needling construction of the batt requires perforating the interior insulating layer, thereby providing numerous passageways for the passage of both heat and sound.
While a number of adhesives, adhesive webs and binding fibers have been specifically developed over the years to secure the various layers of the laminates together, laminated shields and insulators have an inherent risk of delamination and failure. The potential is, in fact, significant mainly due to the harsh operating environment to which the shields and insulators are subjected. Many shields and insulators are located near and/or are designed to shield high heat sources such as the engine, transmission and exhaust system. As a result, the shields and insulators are often subjected to temperatures in excess of 200° F. which have a tendency to degrade the adhesives and binders over time.
Shields and insulators used for under carpet and floor pan applications also carry foot traffic and thus are subjected to repeated compression and decompression. This activity places very significant strain on the shields and insulators, often resulting in adhesive failure and delamination of the shield or insulator over time.
A need is therefore identified for an under carpet heat shield/floor pan insulator incorporating a nonlaminate acoustical and thermal insulating layer of polymer fibers suitable for use in the proximity of high temperature heat sources such as an exhaust system and particularly a catalytic converter and capable of providing the desired acoustical and thermal insulating properties. Advantageously, such an insulator also provides the desired mechanical strength and rigidity to allow simple and convenient installation while also providing a long service life characterized by reliable performance.